In the cosmetics art, emollients are understood to be substances which make the skin more supple and soft, and/or more absorptive of active ingredients and/or which increase the adhesion of decorative cosmetic materials to the skin. Various materials have previously been employed as emollients for the above purposes, including fatty acid esters, such as isopropyl myristate, cetyl lactate and lanolin, including suitable derivatives; glycols and polyglycols; but these materials have frequently led to sensitization reactions which result in allergies. A further significant disadvantage of known emollients is the fact that they tend to interact with emulsifiers and thus impair the stability of cosmetic emulsions, especially the water-in-oil type.
Wool fat and its derivatives have been employed to stabilize water-in-oil emulsions so as to provide water-in-oil emulsions with a reduced tendency toward inversion. However, wool fat and wool fat derivatives have a strong inherent odor and have caused allergic reactions. The relative strong odor, in turn, requires a strong perfume, causing additional problems for persons with sensitive skin.
Attempts have previously been made to replace wool fat derivatives with ethylene oxide/propylene oxide block copolymers. However, the resultant water-in-oil emulsions lack storage stability, and display a strong tendency to invert to oil in water emulsions.
Water-in-oil emulsions have previously been formulated for cosmetic purposes employing the reaction product of wool fat and ethylene oxide/propylene oxide block copolymers in place of wool fat. However, the reaction products did not eliminate the disadvantages of wool fat. Therefore, recently, especially in view of the allergenic effect of wool fat derivatives, numerous attempts have been made to find polymers that do not display the disadvantages of wool fat and its derivatives and would allow elimination of wool fat and its derivatives in cosmetic water-in-oil emulsions. Examples of polymers considered include copolymers of acrylamide and alkylvinyl carboxylic esters, copolymers or terpolymers of N-vinyl pyrrolidone and alkylcarboxylic vinyl esters, copolymers or terpolymers of N-vinylimidazole, alkyl(meth)acrylates, containing 6 to 24 carbon atoms in the alkyl group or a crcloalkyl group, and optionally vinyl acetate.